in disturbed areas, and in areas where 

 Thalassia or Syringodium are excluded 

 because of the prevailing conditions. 

 Shoal grass grows connonly in water either 

 too shallow or too deep for these sea- 

 grasses. Leaves are flat, typically 1 to 

 3 mm wide and 10 to 20 cm long, and arise 

 from erect shoots. The tips of the leaves 

 are not rounded, but have two or three 

 points, an important recognition charac- 

 ter. Halod ule is the most tolerant of all 

 the seagrasses to variations in tempera- 

 ture and salinity (Phillips 1960; r^lcMillan 

 and Moseley 1967). In low salinity areas, 

 care must be taken to avoid confusing it 

 with Ruppia. 



Three species of Halophila , all small 

 and delicate, are sparsely distributed in 

 south Florida. Halophila engelmanni is 

 the most recognizable with a whorl of four 

 to eight oblong leaves 10 to 30 mm long 

 borne on the end of a stem 2 to 4 cm long. 

 This species has been recorded from as 

 deep as 90 m (295 ft) near the Dry Tortu- 

 gas. Halophila decipiens has paired 

 oblong-elliptic leaves 10 to 25mm long 

 and 3 to 5 mm wide arising directly from 

 the node of the rhizome. A new species. 



\j_. Johnson i i , was described (Eiseman and 

 McMillan 1980) and could be easily confus- 

 ed with jH. decipiens. The most obvious 

 differences are that _H. john sonii lacks 

 hairs entirely on the leaf surface and the 

 veins emerge from the midrib at 45° angles 

 instead of 60°. The initial description 

 recorded H^. johns onii from Indian River to 

 Biscayne Bay, but its range could ulti- 

 mately be much wider. 



The major problem in positive identi- 

 fication of seagrasses is between Halodule 

 and Puppia maritima , commonly known as 

 widgeongrass. Although typically found 

 alongside Halodule , primarily in areas of 

 reduced salinity, Puppia is not a true 

 seagrass, but rather a freshwater plant 

 that has a pronounced salinity tolerance. 

 It is an extremely important food for 

 waterfowl and is widely distributed. 

 Where it occurs, it functions similarly to 

 the seagrasses. In contrast with Halo- 

 dule , the leaves are expanded at the base 

 and arise alternately from the sheath, and 

 the leaf tips are tapered to a long point. 

 It should be noted, however, that leaf 

 tips are commonly missing from older 

 leaves of both species. 



10 



